Large Cell Scope Pictures, Part II - Physics

Large Cell Scope Pictures, Part II This is a follow-up on Richards measurement of large cell signals. In addition to his test I added a small, 7 cm z-strip under the LST. This z-strip is made out of copper tape, about 7x15 cm^2. It is connected via a BNC connector and a 50 Ohm coax cable to a scope (50 Ohm termination) If have updated the two drawings below taken from Richards presentation. Ground plane above cathode and below tube (see picture below) Please note that there is an asymmetry in the chamber endcap: the HV pins are not located at the symmetry line but closer the the bottom of the tube. According to the drawings of the large cell tubes that are available on the web, this is the closed side of the profile. If this is correct, our phi signals come from the open side of the profile, the z signals come from the closed side. phi strip

g ++0++ g g=gas fitting +=HV 0=ground z strip

S1 Phi Cathode signal Gnd HV Z cathode signal 1nF Large Cell Tube S2

S1 S2 Anode signal scope Example 1: Anode at 20 mV, z at 10 mV and phi at 5 mV per division Example 2: Anode at 20 mV, z at 10 mV and phi at 5 mV per division Example 3: Anode at 20 mV, z at 10 mV and phi at 5 mV per division

Conclusion: We see signal in coincidence at both cathodes and the anode Anode signals are the largest. Followed by the z strip signals (which we believe come from the closed side of the profile) which are about the size of the anode signals. The phi signals (which we believe come from the open side of the profile) are about the size of the anode signals. Clearly this is not a complete test. The next step is to measure pulse height spectra for each signal source, check the HV dependency etc.